birds

Shrinking Shorebirds & How Climate is Reshaping Them

/ gtattersall

Shorebirds across Australia are experiencing notable changes in size and shape, offering a vivid example of climate change’s impact on wildlife. In a recent publication in Ecology Letters (McQueen et al), using comprehensive 46-year study involving over 200,000 observations across 25 species we show widespread declines in body size (“shrinking”) and concurrent increases in bill length (“shape-shifting”). These shifts appear to align with thermal adaptation, where smaller bodies and elongated bills would help dissipate heat more effectively in warmer environments. However, we also found that smaller species exhibited the most pronounced changes, while long-distance migratory species showed weaker trends, possibly due to physical constraints needed for efficient flight over vast distances.

Interestingly, while bill lengths have generally increased over time, they shortened following exposure to recent hot summers, hinting at complex evolutionary trade-offs between short-term vs. long-term climatic fluctuations.  We suggest these changes may reflect not only adaptations for thermoregulation but also responses to nutritional stress or other environmental pressures. These findings emphasize the dual role of climate change as both a selective force and a stressor. As global temperatures continue to rise, understanding these morphological changes is crucial for predicting their effects on species survival and the ecosystems they inhabit.

Field sites and climate information for northern and southern Australian shorebird populations. A and B show locations where shorebirds have been sampled by members of the VWSG and AWSG (black circles) and nearby Australian Bureau of Meteorology weather stations with summer temperature data from 1970-2021 (blue triangles); colour scale shows average summer daily maximum temperatures (December-February). 

To read more about the study, it in open access below. 

Citation

A. McQueen, M. Klaassen, G. J. Tattersall, S. Ryding, Victorian Wader Study Group, Australasian Wader Studies Group, R. Atkinson, R. Jessop, C. J. Hassell, M. Christie, A. Fröhlich, M. R. E. Symonds. 2024. Shorebirds are shrinking and shape-shifting: declining dody size and lengthening bills in the past half-century. Ecology Letters. 27:e14513. https://doi.org/10.1111/ele.14513

Shape-Shifting in the Face of Climate Change: The Long and the Short of How Australian Birds Are Adapting

/ gtattersall

As global temperatures rise, animals are facing mounting pressure to adapt, and Australian birds are no exception. Our recent research (from Sara Ryding’s PhD research) has examined over 5,000 museum specimens, representing 78 bird species across Australia, revealing clear changes in their body and appendage sizes. These changes are aligned with two well-known ecological principles: Bergmann’s rule, which predicts smaller body sizes in warmer climates in endotherms, and Allen’s rule, which argues that animals (namely endotherms) will develop larger appendages to regulate body heat. Consistent with these theories, our study found that birds are experiencing a long-term decrease in body size, particularly in absolute wing length, while their appendages, such as bills and tarsi (leg bones), are getting larger relative to their bodies. This phenomenon, often referred to as “shape-shifting,” is a widespread response to the increasing temperatures driven by climate change.

Interestingly, our research also highlights a more complex picture when it comes to short-term responses. While long-term trends show a clear increase in appendage size to aid thermoregulation, birds displayed smaller appendages in the years following hotter temperatures. This suggests that while birds are gradually adapting to rising temperatures over time, short-term weather events may create different selection pressures that affect growth and development. Factors like food availability and reproductive challenges could contribute to these opposing trends. This study underscores the intricate balance between long-term evolutionary changes and the immediate pressures exerted by fluctuating environmental conditions, offering critical insights into how birds—and potentially other animals—might continue to respond to our rapidly changing world.

For a link to the study, please see the citation below.

Citation

Ryding, McQueen, A, Klaassen, M, Tattersall, GJ, and Symonds, MRE. 2024. Long- and short-term responses to climate change in body and appendage size of diverse Australian birds. Global Change Biology, 30:e17517. https://doi.org/10.1111/gcb.17517